The present invention relates generally to pressure contact connectors, and more particularly to a land grid array (“LGA”) connector that uses a plurality of wires as contacts that are held in a flexible body portion of the connector.
The electronics industry has seen a large growth in the past few years of reduced size electronic devices and appliances, such as laptop computers and the like. The industry is always seeking to reduce the size of these components and to increase their functionality and capability. Both aims are accomplished by increasing the density of circuits on components of the device. Although the number of circuits established on a chip or circuit board may be increased, care must be taken to ensure that a reliable interconnection is established between the high density component and another component of the device.
These high-density interconnections are used for microprocessor, ASIC and other types of chips and may also be used to provide a connector between two circuit boards. Ball Grid Array (“BGA”) packages have been used as high-density interconnections for these type applications. In BGA style packages, pads are formed in a substrate and small, spherical balls of solder are placed in contact with the pads. These balls are then heated to provide connections between the chip and another circuit board. However, these balls often exhibit poor circuit board compliance and mechanical properties in effecting contact between the chip and the opposing circuit board. They are not always suitable to overcome variations that may occur in the substrate printed circuit board. Additionally, once the balls are heated to provide solder connections, the chip cannot be easily removed to correct any defect in the soldering, without reworking all of the solder balls and reflowing the ball grid array to the printed circuit board in another attempt to provide a reliable connection. Thus, it can be appreciated that the use of a BGA solder package does not provide a separable device interface.
Land grid array (LGA) connectors have been developed for such applications and they provide circuit paths between the device and the circuit board involving the use of conductive leads, such as formed metal contacts, that are typically embedded in a rigid plastic substrate to connect lands, or pads on a printed circuit board to the solder balls, or lands, that may be formed on a chip or other device. These lands are formed in a particular pattern in opposition to the solder balls/lands of the component to which the connector is mated. These LGA connectors offer numerous advantages over BGA devices in that they provide to the circuit or system designer, a separable interface between the chip/chip package and a circuit board that BGA devices cannot provide because they are soldered to circuit boards to effect their connections. However, in LGA connectors, each conductive lead must exert a particular spring force that should be maintained in order to establish a reliable interconnection to a device. A clamping force must be exerted against a chip to retain it in contact with the connector. Chips having contacts in excess of 1000 contacts may require a contact force of well over a hundred pounds.
U.S. Pat. No. 4,998,885, issued Mar. 21, 1991 describes such a style of connector in which wires with ball-shaped end portions are embedded within an elastomeric pad. However, the elastomeric pad must be precisely scored to a controlled depth by a laser in the area between the wires in order to increase the flexibility of the wires and the ball-shaped end portions thereof. Cutting these lines too deep in the elastomeric pad presents a risk of weakening the elastomer that supports the wires and possibly create unreliable contacts, in that some of the wires may buckle and thereby not fulfill their individual resilient mating functions. This not only complicates the manufacture of, but also increases the cost of manufacture of such connectors.
The present invention is therefore directed to an improved LGA connector and method of making the connector that overcomes the aforementioned disadvantages.